1. Field of the Invention
The present invention relates to a pointing device for controlling the movement of a cursor on a display of a personal computer and the like.
2. Description of the Related Art
Recently, as a notebook computer (notebook PC) is widely spread, a pointing device including a pointing stick is widely used to control the movement of a cursor on a display of the computer (for example, JP-A-2003-296016).
Since a notebook PC having this pointing device does not require a mouse to move a cursor on the display, this PC is consider not to occupy a space on a desk, so that task space can be reduced, and to have excellent usability at home or office as well as in use during moving by public transportation such as airplanes or trains.
This kind of pointing device is not only applied to a notebook PC, but also used to control the movement of a cursor on a display of a home gaming machine and the like.
A pointing device has configuration in which four displacement sensors configured by strain gauges and the like are arranged on a flexible support plate supporting a pointing stick (hereinafter, referred to simply as “stick”) of the pointing device to constitute a Wheatstone bridge circuit (hereinafter, referred to as “bridge circuit” or “bridge connection”).
Hereinafter, the configuration of a pointing device of a bridge connection configuration will be described in detain with reference to FIG. 3. A pointing device 5 having a bridge circuit shown in FIG. 3 includes a pointing stick (not shown) and a support plate (not shown) supporting the pointing stick. Four strain gauges 55-1, 55-2, 56-1 and 56-2 having resistance values varying according to the motion of the pointing stick are provided in a bridge shape. The output from the four strain gauges 55 and 56 is processed in a microcomputer 51 in the pointing device, is sent from the pointing device 5 to a notebook PC 20 by PS/2 communication, and causes to move a cursor on a display 21 of the notebook PC 20. That is, the operation of the pointing stick causes the cursor of the display 21 of the notebook PC 20 to move in X direction and Y direction, or an oblique direction thereto.
More specifically, the strain gauges 55 and 56 constituting the bridge circuit are provided so as to move the cursor displayed on the display 21 in X direction and Y direction of the display 21.
An output between the strain gauge 55-1 corresponding to a cursor +X direction and the strain gauge 55-2 corresponding to a cursor −X direction is input to the microcomputer 51 of the pointing device as a cursor movement instruction signal of the X direction. An output between the strain gauge 56-1 corresponding to a cursor +Y direction and the strain gauge 56-2 corresponding to a cursor −Y direction is input to the microcomputer 51 as a cursor movement instruction signal of the Y direction of the cursor on the display.
One side of the bridge circuit is connected to the ground GND, and the other side is connected to a power source of about 5 V through a fixed resistor 57. Also, an output between the fixed resistor 57 and the bridge circuit is input to the microcomputer 11 as an instruction signal of the Z direction of the pointing stick.
Thus, in the output of the four sensors of the pointing device having the bridge connection configuration as described above, the output corresponding to the cursor Z direction is directly sent from between the bridge circuit and the fixed resistor 57 to the microcomputer 51, in addition to the output according to the operation of the pointing stick corresponding to the X direction movement instruction of the cursor and the output corresponding to the Y direction movement instruction of the cursor.
Since the cursor Z direction instruction signal is easily (directly) received in the microcomputer 51, the pointing device that sends an operation instruction of the Z direction to the notebook PC as an output signal usually has a bridge connection configuration.
In the meantime, a pointing device having a so-called star connection configuration, in which four strain gauges are provided in parallel is not generally used since it is difficult to sense a stick operation of the Z direction.